This invention relates to an improvement of a contact for an electric connector which includes a socket or the like, and more particularly to a contact for a connector having two contact elements receiving therebetween a thin male contact in the form of a pin of a mating connector.
Conventional contacts for connectors including sockets will be explained referring to FIGS. 1a-1d.
In FIG. 1a, a contact 10 comprises two contact elements 10A and 10B in opposition to each other adapted to receive a male contact (not shown) to be inserted in a direction shown by an arrow 20. The contact 10 is located in an insulating block 13 for insulatingly holding the contact 10 therein.
FIG. 1b illustrates change in position of the contact 10 when the male contact 12 (shown in a dot-and-dash line) is inserted between the opposed contact elements 10A and 10B of the contact 10. The contact 10 is shown in solid lines before the insertion of the male contact and in dot lines after the insertion.
Assuming that the male contact 12 has a thickness T and the contact 10 has the narrowest clearance G between the contact elements 10A and 10B before the male contact 12 is inserted therebetween, a displacement D of each the contact element 10A or 10B upon insertion of the male contact 12 is indicated as an equation (1). ##EQU1##
Moreover, after the insertion, a pressing force P to which the male contact 12 is subjected by both the contact elements 10A and 10B in directions shown by arrows 21 is indicated by an equation (2). ##EQU2## where K is a constant.
In case of a contact shown in FIG. 1c, projections 11A and 11B at distal ends of the contact elements 10A and 10B of the contact 10 extend toward each other. In producing this contact, after the contact 10 shown in FIG. 1c has been obtained by punching a thick plate in a press, the contact elements 10A and 10B are hammered in directions shown by arrows 22 to narrow a clearance G therebetween.
The minimum values of the clearances G in FIGS. 1a and 1c are zero.
In case of a contact shown in FIG. 1d, contact elements 10A and 10B have different lengths L.sub.1 and L.sub.2, to permit protrusions 11A and 11B to overlap each other, so that a value of clearance G between the contact elements can be negative. In this case, "negative" means that the protrusions overlap each other.
With the contacts 10 shown in FIGS. 1a and 1c, as the minimum values of the clearance G are zero, it encounters a great difficulty to produce contacts whose clearances G are near to zero. Moreover, the male contact is generally required to be thin as much as possible in order to achieve miniaturization and light weight of the connector to save resources and lower manufacturing cost.
As can be seen from the equation (2), however, even if the clearance G is zero, the pressing force P for embracing the male contact 12 becomes zero or near to zero, when the thickness T of the male contact is near to zero. Such a slight pressing force in conjunction with errors in assembling and molding would give rise to great problems such as incorrect or insufficient contact between the male and female contacts.
With the contact as shown in FIG. 1a, moreover, there is a problem in that when the clearance G is zero, contacting portions of the contact elements are not plated in plating after molding. In order to avoid this problem, it has been proposed to working a plated thin plate by pressing into the shape as shown in FIG. 1a. According to this proposal, cut surfaces are devoid of plating layers and bent portions are like to be scratched.
In order to solve these problems, the contact as shown in FIG. 1d has been used. In this case, the problem of insufficient contact is solved because of the negative clearance G. As can be seen from the drawing, however, the contact elements 10A and 10B are often twisted by the insertion of the male contact. Moreover, even if the male contact 12 is inserted correctly in an axial direction of the contact 10, the male contact 12 would be subjected to a force causing the male contact 12 to be tilted. Accordingly, guides on the insulating block are needed in order to maintain the direction of the insertion of the male contact correctly. Moreover, as the contact elements 10A and 10B have the different lengths L.sub.1 and L.sub.2, it is usual to select the shorter length L.sub.2 first of all so as to obtain a required pressing force P, and then the longer length L.sub.1 is determined. As a result, the length L.sub.1 is apt to become longer and obstructs the miniaturization of the connector.